Image pickup device with automatic and manual exposure control modes for image signal and image display to display an image based on an image signal obtained in automatic or manual exposure control

ABSTRACT

An image pickup device designed to always ensure improved facility with which an object is recognized even in a manual exposure control mode. The image pickup device includes an exposure control device capable of being selectively set in one of an automatic mode and a manual mode, and an operating member for starting processing and storage of an image signal. In this image pickup device, to achieve the above-mentioned effect, an image obtained in the automatic mode is displayed immediately before the operation of the operating member even in a case where photographing is performed in the manual mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup device capable ofoperating in a mode selected from a plurality of exposure control modesincluding a manual exposure control mode, and to a computer-readablestorage medium on which a program for controlling the image pickupdevice is stored.

2. Related Background Art

Recent automated cameras have a system for automatically determining theamount of exposure by using a central processing unit (CPU) incorporatedin the camera. Such a system enables easier photographing in each of anaperture value priority mode, a shutter speed priority mode, a mode ofphotographing based on a predetermined program diagram (program), etc.

Some electronic cameras using an image pickup element such as acharge-coupled device (CCD) are designed so that the image pickupelement is also used as a photometric sensor for the purpose of reducingthe manufacturing cost. In such cameras, since the image pickup elementis used as a photometric sensor, signals representing data, for example,on image brightness, colors, and sharpness are extracted from an imageimaged on the image pickup element, and control operations, such asautomatic exposure, white balancing, automatic focusing and strobe lightcontrol are performed on the basis of the signals.

An image imaged on the image pickup element is output through an imageoutput device, such as an electronic view finder using a liquid crystaldisplay (LCD) or the like, or a video output device. When an operatorchecks the image imaged on the image pickup element, for example, byoutputting the image through the image output device, exposure controlfor maintaining the main object at a certain brightness level isrequired.

On the other hand, the operator can make the camera perform automaticexposure control after selecting at least one of desirable exposurecontrol values: an aperture value AV, a shutter speed TV, and asensitivity SV and selecting one of exposure control modes, such as anaperture value priority mode and a shutter speed priority mode. Theoperator can also make the camera perform exposure control with valuesall set by the user in a manual mode or the like.

The operator can also make the camera perform automatic exposure controlin a photographing mode in which a shutter speed or an apertureselection effect can be obtained while no exposure control value isdesignated, e.g., a high-speed shutter mode using a program diagram suchthat a higher shutter speed is set, or a landscape mode using a programdiagram such that a smaller aperture value is set.

The operator can also make the camera perform light control duringphotographing using a strobe in such a manner that photometry isperformed when a strobe does not emit light to an object and when thestrobe emits light as a pre-emission to the object, and the reflectivityof the object is computed from the difference between the two photometryresults to determine the quantity of light to be emitted at the time ofactual photographing. It is, of course, possible for the operator toperform a manual control operation for determining the quantity of lightto be emitted by the strobe.

However, in taking a picture of an object under some conditions,including a selected exposure control value, there is a possibility offailure to display an image on an image output device suitably enough toensure sufficient facility with which the image is framed.

In particular, a photographing operation that presupposes the use ofstrobe light may require an underexposure setting, depending on thequantity of strobe light. In such a case, if exposure control isperformed without regard to the underexposure condition, the image isdisplayed in a dimmed condition on the image output device and cannot beeasily framed.

For example, in a case where there is a difference between the aperturevalue AV, the shutter speed TV and the sensitivity SV set with respectto an object in automatic-exposure photographing and the aperture valueAV, the shutter speed TV and the sensitivity SV set with respect to theobject in photographing with strobe light, a difference in brightness ofthe images output to image output device may occur between these twophotographing modes. In contrast to automatic exposure, a certain amountof underexposure is ordinarily set in photographing with strobe light byconsidering the superimposition of the quantity of strobe light on anobject. Therefore, when the aperture value AV, the shutter speed TV,etc., are set with respect to an object in photographing with strobelight, the amount of underexposure may be considerably large, dependingon conditions relating to the object.

SUMMARY OF THE INVENTION

In view of the above-described circumstances, an object of the presentinvention is to provide an image pickup device in which, even when amanual exposure mode is selected, automatic exposure control isperformed by ignoring a set exposure control value to ensure improvedfacility with which an object is recognized as well as facility withwhich framing is performed.

According to the present invention, there is provided an image pickupdevice including: an image pickup element which receives light from anobject to form an image signal; an exposure control device; a devicecapable of setting an automatic exposure control mode and a manualexposure control mode as a mode of operation of the exposure controldevice; and a photographing initiation operating member for initiatingprocessing and storage of the image signal output from the image pickupelement, in which even when the manual exposure mode is set, the imagepickup element outputs the image signal in association with the exposurecontrol device operating in the automatic exposure control mode beforethe photographing initiation operating member is operated.

According to another aspect of the present invention, there is providedan image pickup device including: an image pickup element which receiveslight from an object to form an image signal; an exposure controldevice; a device capable of setting an automatic exposure control modeand a manual exposure control mode as a mode of operation of theexposure control device; a photographing initiation operating member forinitiating processing and storage of the image signal output from theimage pickup element; and a selection device capable of selectingbetween outputting of the image signal from the image pickup element inassociation with the exposure control device operating in the automaticexposure control mode and outputting of the image signal from the imagepickup element in association with the exposure control device operatingin the manual exposure control mode before the photographing initiationoperating member is operated, even if the manual exposure control modeis set.

Also, according to another aspect of the present invention, there isprovided an image pickup device including: an image pickup element whichreceives light from an object to form an image signal; an exposurecontrol device; a device capable of setting an automatic exposurecontrol mode and a manual exposure control mode as a mode of operationof the exposure control device; a photographing initiation operatingmember for initiating processing and storage of the image signal outputfrom the image pickup element; and a selection device capable ofselecting, according to whether photographing with strobe light can beperformed, between outputting of the image signal from the image pickupelement in association with the exposure control device operating in theautomatic exposure control mode and outputting of the image signal fromthe image pickup element in association with the exposure control deviceoperating in the manual exposure control mode before the photographinginitiation operating member is operated.

Also, according to another aspect of the present invention, there isprovided a computer-readable storage medium having a program forcontrolling an image pickup device having an image pickup element whichreceives light from an object to form an image signal, an exposurecontrol device, a device capable of setting an automatic exposurecontrol mode and a manual exposure control mode as a mode of operationof the exposure control device, and a photographing initiation operatingmember for initiating processing and storage of the image signal outputfrom the image pickup element, the program including the step of:executing, when the manual exposure control mode is set, selectionprocessing enabling selection between outputting of the image signalfrom the image pickup element in association with the exposure controldevice operating in the automatic exposure control mode and outputtingof the image signal from the image pickup element in association withthe exposure control device operating in the manual exposure controlmode before the photographing initiation operating member is operated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a construction of an image pickupdevice;

FIG. 2 is a flowchart for explaining processing in a manual exposurecontrol mode in an embodiment of the present invention; and

FIG. 3 is a flowchart for explaining processing in a manual exposurecontrol mode in another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An image pickup device, a method of controlling the image pickup device,a program, and a computer-readable storage medium in accordance with thepresent invention will be described with reference to the accompanyingdrawings.

FIG. 1 is a block diagram showing a construction of the image pickupdevice. This image pickup device is capable of moving imagephotographing as well as still image photographing and is also capableof selecting a manual exposure control mode in which manual exposurecontrol can be performed. Referring to FIG. 1, the image pickup devicehas a lens 100 constituting a photographing optical system, a controlmotor 101 for driving the lens 100, and a motor driver 102 whichfunctions as a lens drive means for driving the control motor 101.

The image pickup device also has a diaphragm 103, a control motor 104for driving the diaphragm 103, and a motor driver 105 which functions asa diaphragm drive means to drive the control motor 104.

The image pickup device also has an image pickup element 107 which isprovided as an image pickup device, and which is constituted by a CCD orthe like capable of photoelectric conversion of light incident thereon,and a shutter drive circuit 106 which functions as an accumulation timecontrol means for controlling the accumulation time of charge to beconverted by photoelectric conversion in the image pickup element 107.

The image pickup device further has a signal amplifying circuit 108 suchas an automatic gain control (AGC) which changes the gain of a signaloutput from the image pickup element 107, a signal processing circuit109, and a strobe control part 110 for controlling a strobe (not shown).

The image pickup device further has a CPU 111 which performs overallcontrol of the image pickup device by performing computationalprocessing, and a shutter switch 112 for inputting an instruction tostart photographing. When the shutter switch 112 is moved to anintermediate operating position (half-pressed), a shutter switch SW1 isturned on to initiate an operation such as automatic exposureprocessing. When the operation of the shutter switch 112 is completed(fully depressed), a shutter switch SW2 is turned on to initiate asequence of operations including a normal exposure operation, an imageprocessing operation in the signal processing circuit 109, and storagein an image record medium 113 of a signal obtained as a result of imageprocessing.

In the thus-arranged image pickup device, an optical signal which haspassed through the lens 100 is converted into an electrical signal inthe image pickup element 107, and this signal is input to the signalprocessing circuit 109 via the signal amplifying circuit 108.

The CPU 111 performs exposure control. To perform aperture control, theCPU 111 controls opening/closing of the diaphragm 103 making the motordriver 105 drive the control motor 104 on the basis of an aperture valueAV.

To perform shutter speed control, the CPU 111 controls the time foraccumulation of charge in the image pickup element 107 (i.e., the amountof accumulated charge) by controlling the shutter drive circuit 106 onthe basis of a shutter speed TV. Thus, the circuit 106 functions as anaccumulation time control means.

To control the signal amplifying gain, the CPU 111 controls the signalamplifying circuit 108 on the basis of a gain value. The signal inputfrom the image pickup element 107 is amplified by the signal amplifyingcircuit 108 on the basis of the gain set by the gain control.

To perform automatic exposure control in an automatic exposure controlmode, a brightness level signal indicating the current brightness signallevel is extracted from the signal input to the signal processingcircuit 109 and is input to the CPU 111. The CPU 111 performs aphotometry operation on the basis of this brightness level signal toobtain an object brightness BV. While use of the image pickup element107 as a photometry means has been described, a sensor or the like forphotometry only may alternatively be used to enable the objectsensitivity BV to be obtained. Also, when the photometry operation isperformed, weighting of a measured light distribution may be changed bybeing linked to the automatic focusing frame (AF).

On the basis of the object brightness BV obtained as described above,the aperture value AV, the shutter speed TV and the gain value aredetermined from a program diagram in which the relationships between thesensitivity SV, the aperture value AV, the shutter speed TV, and thegain value are prescribed. The diaphragm, the aperture value, theshutter speed, and the gain are controlled on the basis of the controlvalues, thus performing exposure control.

The signal from the image pickup element 107 on which exposure controlhas been performed as described above is processed in the signalprocessing circuit 109 to form an image signal to be output to an imageoutput device 114 which is an electronic view finder, a video outputdevice, or the like.

The CPU 111 can also control charging on a main capacitor 115 of thestrobe control part 110, which accumulates charging voltage for strobeemission. The CPU 111 performs this control by supplying the strobecontrol part 110 with a pulse signal for charging or a reference voltagefor charging. The selection of the method of this charging depends onthe construction of the strobe control part 110. When the main capacitor115 has a sufficient amount of charge, the CPU 111 can perform emissioncontrol by supplying a trigger signal to the strobe control part 110.

Processing in the manual exposure control mode in an embodiment of thepresent invention will be described with reference to the flowchart ofFIG. 2. When an operator changes the exposure control mode to enablemanual exposure (setting of the manual exposure control mode) andselects and sets an aperture value AV and a shutter speed TV, a check ismade to determine whether automatic exposure display setting has beenselected (step S100). Automatic exposure display setting may be selectedby the operator using an operating member (not shown) for this settingor may be automatically set when photographing with strobe light isselected.

A detachably mountable external strobe whose charging state can bedetected, for example, by communication or by checking a voltagecondition at a terminal other than the X-contact of the accessory shoecan be operated in the same manner as the strobe incorporated in thecamera. Even in a case where the state of charge in a strobe cannot bedetected from the camera side, as in a detachably mountable externalstrobe having no control means other than the X-contact, a determinationcan be made as to whether strobe emission control can be performed, if adetection device, such as a switch, detects a state where an externalstrobe is attached to the accessory shoe. Even in such a case,therefore, the strobe can be operated in the same manner.

If an automatic exposure display setting has been selected, automaticexposure is performed (step S101) to output a suitable moving imagethrough the image output device 114. If an operation accompanied byexposure correction is performed, a correction device may be provided toperform exposure correction, for example, according to the subjectdistance. In such a case, if the subject distance cannot be determined,exposure correction is not performed. Alternatively, exposure correctionmay be performed according to the position of the zoom lens and theposition of the focusing lens of the lens 100. Alternatively, exposurecorrection may be performed according to the sensitivity. Alternatively,exposure correction may be performed in a case where lighting correctionis made. Alternatively, exposure correction may be performed accordingto the quantity of light emitted at the time of photographing.

If automatic exposure display setting has not been selected, exposurecontrol is performed with manually set exposure value EV (step S102). Inthis case, if the operator can set the sensitivity SV for actualphotographing, the exposure value EV may be computed by considering thesensitivity in the current operation mode to enable exposure control.

The state of the shutter switch SW2 is then checked as to whether theshutter switch SW2 has been turned on (step S103). If the shutter switchSW2 is not turned on, the process returns to step S100 and the stepsdescribed above are repeated. If the shutter switch SW2 is turned on,the aperture value AV and the shutter speed TV manually preset are setinto each device (step S104). The exposure operation for actualphotographing is then started (step S105), followed by photographingwith strobe emission.

The above-described processing ensures that even when the manualexposure control mode is set, either of automatic exposure control andmanual exposure control can be selected before the operation of theshutter switch SW2, and that, if automatic exposure control is performedbefore the shutter switch SW2 is turned on, an image is displayed on theimage output device 114 with such a brightness that the main object canbe recognized immediately before the photographing operation is started,thus improving the operability with respect to framing.

Photographing with strobe emission in the manual exposure control isperformed as described above. However, it is also possible to improvethe operability with respect to framing in the case of photographingwithout strobe emission by using a similar procedure. The exposurecontrol at that time can be performed by a manual or automaticoperation.

In a case where an aperture shutter capable of a fully closing operationis used, because the maximum speed of the shutter speed becomes fasteras the aperture diameter becomes smaller, if the shutter speed TV is setto 1/1000 when the aperture value AV is smaller than F8, the aperturevalue AV is limited to F8 if 1/1000 is designated in the shutter speedpriority mode, even in a situation where maximum-aperture setting shouldbe made. If exposure control is performed under such a condition, thereis a possibility of difficulty in performing framing as in the case ofphotographing with strobe emission, depending upon the condition of theobject. In such a situation, the image pickup device may be operated inthe same manner to achieve the same effect.

In such a case, however, if exposure control is performed withoutconsideration of the exposure value EV at the time of photographing whenthe shutter switch SW1 is depressed, it is possible that the brightnessat the time of actual photographing will differ greatly from the desiredvalue so as to cause distortion in the operator's recognition of thedisplayed image. Therefore it is effective to use an arrangement inwhich an operating member (not shown) such as a switch is separatelyprepared and functions are changed by an input from the operatingmember, or to use a method of displaying information about thedifference of the recognized brightness from that at the time of actualphotographing to warn the operator of the undesirable condition.

Processing in the manual exposure control mode in another embodiment ofthe present invention will be described.

When forced strobe emission or automatic strobe emission is selected andwhen the brightness is low, photographing using the strobe is performed,provided that the main capacitor 115 of the strobe control part 110 issufficiently charged to cause the strobe to emit light. Under thiscondition, automatic exposure is performed to output a suitable movingimage through the image output device 114, as described above in thedescription of the first embodiment.

However, when the amount of charge on the main capacitor 115 isinsufficient, photographing with strobe light cannot be performed. If,in such a situation, a moving image is displayed on the image outputdevice 114 by performing automatic exposure control, there is a risk ofallowing the operator to erroneously recognize that photographing withstrobe emission will be performed.

When the shutter switch SW2 is turned on in such a situation, theprocess described above in the description of the first embodiment maybe performed if photographing is performed after waiting for thecompletion of sufficient charging on the main capacitor 115. However, ifthe time before the completion of charging is long, the shutter chanceis missed. In some cases, by considering this problem, photographingbased on automatic exposure is performed without causing the strobe toemit light.

In the case of a strobe incorporated in the camera that uses powersupplied from an internal power supply of the camera, the time beforethe completion of charging can be predicted by the CPU 111. In contrast,an external strobe, for example, ordinarily uses an external powersource different from that in the camera. The CPU 111 cannot predict thetime before the completion of charging in such an external strobe. Insuch a case, it is impractical to wait for the completion of charging,and photographing based on automatic exposure control is thereforeperformed.

Processing in the manual exposure control mode performed by consideringthe above-mentioned points will be described with reference to theflowchart of FIG. 3. In FIG. 3, steps corresponding to those shown inthe flowchart of FIG. 2 are indicated by the same reference characters.

When an operator changes the exposure control mode to enable manualexposure (setting of the manual exposure control mode) and selects andsets an aperture value AV and a shutter speed TV, a check is made todetermine whether charging on the main capacitor 115 of the strobe hasbeen completed (step S200). If charging on the main capacitor 115 hasbeen completed, photographing with strobe light can be performed andautomatic exposure control is therefore performed (step S101). Ifcharging on the main capacitor 115 has not been completed, exposurecontrol is performed by using the set exposure value EV (step S1102).

The state of the shutter switch SW2 is then checked as to whether theshutter switch SW2 has been turned on (step S103). If the shutter switchSW2 is not turned on, the process returns to step S200 and the stepsdescribed above are repeated. When charging on the main capacitor 115 iscompleted while these steps are being repeated, automatic exposurecontrol is performed and a bright image is output through the imageoutput device 114, thereby enabling the operator to know the completionof charging on the main capacitor 115. Thus, the operator can determinefrom the state of the output image whether photographing with strobelight will be performed.

When the shutter switch SW2 is turned on, the aperture value AV and theshutter speed TV manually preset are set into each device (step S104). Acheck is then made to determine whether charging on the main capacitor115 has been completed (step S201). If charging on the main capacitor115 has been completed, photographing with strobe light can be performedand photographing with strobe emission is therefore performed (stepS202). If charging on the main capacitor 115 has not been completed,photographing without strobe emission is performed (step S203).

The present invention includes, within its scope, an implementation of amethod in which program codes of software for realizing the functions ofeach of the above-described embodiments of the present invention aresupplied to a computer in an apparatus or a system connected to variousdevices and capable of operating the devices so as to realize thefunctions of the embodiment, and in which the various devices areoperated on the basis of a program stored in the computer (CPU or MPU)of the system or apparatus.

In such a case, the program codes themselves of the above-mentionedsoftware realize the functions of each of the above-describedembodiments, and the program codes themselves constitute the presentinvention. As a medium for transmission of the program codes, acommunication medium (a cable such as an optical fiber cable, a wirelesschannel, or the like) in a computer network (a LAN, a WAN such as theInternet, a wireless communication network, or the like) system forsupplying program information by transmitting the same on a carrier wavemay be used.

Further, means for supplying the program codes to the computer, e.g., astorage medium on which the program codes are stored constitutes thepresent invention. As the storage medium for storing the program codes,a flexible disk, a hard disk, an optical disc, a magneto-optical disc, acompact disc-read only memory (CD-ROM), a magnetic tape, a nonvolatilememory card, a ROM, etc., may be used.

Needless to say, the present invention includes, in its embodiments,program codes not only in a case where the program codes supplied to acomputer are executed by the computer to realize the functions of eachof the above-described embodiments, but also in a case where the programcodes are used in association with an operating system (OS) or a pieceof application software running on a computer.

Further, needless to say, the present invention comprises realization ofthe functions of each of the above-described embodiments achieved byperforming processing in such a manner that supplied program codes arestored in a memory provided in a function expansion board of a computeror a function expansion unit connected to the computer, and a CPU or thelike provided in the function expansion board or the function expansionunit performs part or the whole of actual processing on the basis ofinstructions according to the program codes.

The configuration and structure of the components of the embodimentsdescribed above have been shown only as an example in implementation ofthe present invention, and are not to be construed as limiting thetechnical scope of the present invention. That is, the present inventioncan be implemented in various forms without departing from essentialfeatures thereof.

According to the above-described embodiments, even in a situation wherean image is not correctly displayed on an image output device undercertain conditions including a manually set exposure control value,automatic exposure control is performed to display the image with such abrightness that the main object can be recognized immediately before thephotographing operation is started, thus improving the objectrecognition and improving the operability with respect to framing.

1. An image pickup device comprising: an image pickup element which receives light from an object and outputs an image signal in response to receiving the light from the object; an exposure control device; a setting device capable of setting an automatic exposure control mode and a manual exposure control mode, as modes of operation of the exposure control device; a display device which processes the image signal output from the image pickup element and displays an image on the basis of the processed image signal; and a photographing initiation operating member configured to initiate processing and storage of the image signal output from said image pickup element, and wherein before operating the photographing initiation operating member in a case of setting the manual exposure control mode, the automatic exposure control mode can be set by the setting device so as to cause the display device to display the image based on the image signal which is obtained in the automatic exposure control, and before operating the photographing initiation operating member in a case of setting the manual exposure control mode, the manual exposure control mode can be set by the setting device so as to cause the display device to display the image based on the image signal which is obtained in the manual exposure control, wherein, before operating the photographing initiation operating member in a case of setting the manual exposure control mode, when photographing with strobe light is performed, the display device displays the image based on the image signal which is obtained in the automatic exposure control.
 2. An image pickup device comprising: an image pickup element which receives light from an object and outputs an image signal in response to receiving the light from the object; an exposure control device; a setting device capable of setting an automatic exposure control mode and a manual exposure control mode, as modes of operation of the exposure control device; a display device which processes the image signal output from the image pickup element and displays an image on the basis of the processed image signal; a photographing initiation operating member configured to initiate processing and storage of the image signal output from said image pickup element, and wherein before operating the photographing initiation operating member in a case of setting the manual exposure control mode, the automatic exposure control mode can be set by the setting device so as to cause the display device to display the image based on the image signal which is obtained in the automatic exposure control, and before operating the photographing initiation operating member in a case of setting the manual exposure control mode, the manual exposure control mode can be set by the setting device so as to cause the display device to display the image based on the image signal which is obtained in the manual exposure control; and a check circuit configured to check whether a photographing operation with strobe light can be performed in the manual exposure control mode, wherein, before operating the photographing initiation operating member in a case of setting the manual exposure control mode, the display device displays the image based on the image signal which is obtained in the automatic exposure control in a case where the check circuit determines that the photographing operation with strobe light can be performed.
 3. An image pickup device according to claim 2, wherein said check circuit checks whether the photographing with strobe light is performable by checking whether charging of a strobe has been completed.
 4. An image pickup device comprising: an image pickup element which receives light from an object and outputs an image signal in response to receiving the light from the object; an exposure control device; a setting device capable of setting an automatic exposure control mode and a manual exposure control mode, as modes of operation of the exposure control device; a display device which processes the image signal output from the image pickup element and displays an image on the basis of the processed image signal; a photographing initiation operating member configured to initiate processing and storage of the image signal output from said image pickup element; and a selection device configured to select, before the operating of the photographing initiation operating member, between plural images to be displayed on the display device, one of which is formed on the basis of the image signal obtained in the automatic exposure control and the other of which is formed on the basis of the image signal obtained in the manual exposure control when a photographing operation with a strobe light is to be performed, wherein said selection device selects as the image to be displayed on the display device the image formed on the basis of the image signal obtained in the automatic exposure control in a case where the photographing operation with the strobe light can be performed, and selects the image formed on the basis of the image signal obtained in the manual exposure control in a case where the photographing operation with strobe light can not be performed. 